Internal fans loud but no output to monitor

[Renfield-64]

Hi,

I have a PC that when powered on gives no output to the monitor but the internal fans are unusually loud, I have had the lid off and cleared away any dust etc from the inside of the PC but it doesn't make any difference. I have also tried re-seating the RAM. There doesn't seem to be any HDD activity going on.

 

I am sure I have had this problem with PCs in the past but can't remember if I solved it or not.

 

Any ideas?

[Rob_D]

Sounds like the PC isn't posting right (or at all).

Maybe try resetting the CMOS.

We used to have a bunch of computers that would do that a lot, and unplugging the power cable for a couple of minutes (or the amount of time it takes to carry it back to the office) seemed to get it to boot.

[Renfield-64]

Hi,

I did have it completely disconnected for about 10 minutes whilst I cleaned out the inside. No luck.

[LeMarchand]

Sounds like the PC isn't posting right (or at all).

Maybe try resetting the CMOS.

 

Thanks. Noticed a suite machine was running very loud with no display or LEDs last night, and couldn't get it to POST today. Clearing the CMOS did the trick.

[LeMarchand]

Well, that lasted until I took the machine back to the suite and plugged it back in .

[Domino]

Well, that lasted until I took the machine back to the suite and plugged it back in .

 

I once had a machine that was doing that. Turned out to be the USB mouse at that desk was knackered and causing a POST fail. Never seen it before or since.

[chazzy2501]

yes, make sure there are no shorts. a loose screw in the PC, shorted mangled usb ports and broken peripherals. (I've had cables torn out of mice and keyboards then stuffed back in so they look ok)

[bknaggs]

Hi,

I have a PC that when powered on gives no output to the monitor but the internal fans are unusually loud, I have had the lid off and cleared away any dust etc from the inside of the PC but it doesn't make any difference. I have also tried re-seating the RAM. There doesn't seem to be any HDD activity going on.

 

I am sure I have had this problem with PCs in the past but can't remember if I solved it or not.

 

Any ideas?

 

We had this problem with a batch of PCs and it turned out to be the power supplies.

[LeMarchand]

I once had a machine that was doing that. Turned out to be the USB mouse at that desk was knackered and causing a POST fail. Never seen it before or since.

 

yes, make sure there are no shorts. a loose screw in the PC, shorted mangled usb ports and broken peripherals. (I've had cables torn out of mice and keyboards then stuffed back in so they look ok)

 

Alas, nothing that simple. Luckily the cases are designed so that the kids can't get to the ports and the "device ends" are good (and it won't boot with other kb/mice).

 

We had this problem with a batch of PCs and it turned out to be the power supplies.

 

This is looking likely; it was recently fixed under warranty and the PSU replaced. Maybe the supplier has a bad batch. Time to RMA it, I guess.

[Renfield-64]

I've tried disconnecting USB stuff and it's not that. Might have to swap the PSU.

[E_G_R2]

Not Lenovo's are they? I have it quite often with my older Lenovo's, an unplug and walk to the office usually does the job.

[Renfield-64]

No not Lenovos, I don't think Lenovo existed when these were made!

[bknaggs]

Not Lenovo's are they? I have it quite often with my older Lenovo's, an unplug and walk to the office usually does the job.

 

Ours were Fujitsus.

[Renfield-64]

Yes these are Fujitsus.

[bknaggs]

Which model are you having problems with? Ours was a batch of Esprimo E3521 specifically with rev 03 power supplies. The power supplies from the previous years model were rev 01 and are still working fine.

[Renfield-64]

Yes it is a E3521 model.

[NetworkServices]

If you have a spare power supply, hook that up and see if it posts. The symptom you describe is typical of failed power supply capacitors. If you're electronically minded and comfortable about working safely around switch mode power supplies you can open it up and look to see if any of them have burst, are leaking or have bulging tops. Of course the proper way to test them is with an ESR meter.

[LeMarchand]

My one mysteriously started working today, and I couldn't get it to fault again. Suspect it won't be long before it starts playing up, though.

[difinity]

Heat can temporarily cause a failing capacitor to start, an often used trick if capacitors are suspected and speed is of the essence.

Using a failing power supply is no good for the motherboard and hard drive/ssd attached and could cause it permanent damage. Capacitors smooth voltage spikes, if they are failing those spikes get through to the delicate electronics.

I visually inspect inside power supplies now when I get PCs in for a service, anything over 5 years old.

Any doubts and I check the voltages on my oscilloscope.

[Renfield-64]

Hi,

great I'll have a look,

Thanks,

[LeMarchand]

Heat can temporarily cause a failing capacitor to start

 

That would make sense in my case - will pull the machine on Weds and take another look.

[Zourous]

Brings back memories of my woes....

 

http://www.edugeek.net/forums/hardware/110579-anyone-have-these-fujitsu-esprimo-e3521-desktops.html

[Zourous]

Long story short though, it is the PSU's at fault. When they first show the issue you might get away with a reboot. As time goes by they won't power back on for longer and longer periods. Not a great solution but if you turn the PSU switch off at the end of the day the PC will boot the next time round, but it's either that or fork out for new PSU's which aren't cheap.